Exemplary embodiments disclosed herein generally relate to electrostatographic imaging machines and, more particularly, to an assembly and method for reducing shaft deflection in a stripper roller employed within such a machine.
Flexible electrostatographic imaging members, including flexible electrostatographic imaging belts, are well known in the art. Typical electrostatographic imaging members include, for example, photoreceptors for electrophotographic imaging systems and electroreceptors such as ionographic imaging members for electrographic imaging systems. These imaging members generally comprise at least a supporting substrate layer and at least one imaging layer comprising thermoplastic polymer matrix material. The “imaging layer” as employed herein is generally defined as the dielectric imaging layer of an electroreceptor or the photoconductive imaging layer of a photoreceptor. In a photoreceptor, the photoconductive imaging layer may comprise only a single photoconductive layer or a plurality of layers such as a combination of a charge-generating layer and a charge transport layer.
Generally, in the art of electrophotography, the process of electrophotographic copying is initiated by exposing a light image of an original document onto a substantially uniformly charged photoreceptive member, such as a flexible electrostatographic imaging belts. Exposing the charged photoreceptive member to a light image discharges a photoconductive surface thereon in areas corresponding to non-image areas in the original document while maintaining the charge in image areas, thereby creating an electrostatic latent image of the original document on the photoreceptive member. This latent image is subsequently developed into a visible image by depositing charged developing material onto the photoreceptive member surface such that the developing material is attracted to the charged image areas on the photoconductive surface. Thereafter, the developing material is transferred from the photoreceptive member to a receiving copy sheet or to some other image support substrate, to create an image, which may be permanently affixed to the image support substrate, thereby providing an electrophotographic reproduction of the original document. In a final step in the process, the photoconductive surface of the photoreceptive member is cleaned with a cleaning device, such as elastomeric cleaning blade, to remove any residual developing material which may be remaining on the surface thereof in preparation for successive imaging cycles.
The electrostatographic copying process described hereinabove, for electrophotographic imaging, is well known and is commonly used for light lens copying of an original document. Analogous processes also exist in other electrostatographic printing applications such as, for example, digital laser printing where a latent image is formed on the photoconductive surface via a modulated laser beam, or ionographic printing and reproduction where charge is deposited on a charge retentive surface in response to electronically generated or stored images.
When employed in electrostatographic imaging machines, flexible electrostatographic imaging belts are typically rotatably mounted and driven to transport a receptor portion or surface of the belt (e.g., a photoreceptor surface for an electrophotographic imaging system or an electroreceptor surface for an electrographic imaging systems) through the various processing stations of the imaging machine. These processing stations can include, for example, uniformly charging the belt receptor surface, exposing the charged belt receptor surface to create a latent image on the belt receptor surface, developing the latent image by selectively depositing charged developing material onto the belt, transferring the developing material to a receiving sheet or some other image support substrate, and cleaning the belt to prepare the surface for a successive imaging cycle. To rotatably mount, drive and support the belt in the imaging machine, a number of backer bars and small diameter belt support rollers can be employed, including a tension roller for maintaining the belt under tension, at least one drive roller for driving the belt and a stripper roller.
In addition to rotatably mounting the belt within an imaging machine, the stripper roller functions to strip or separate the receiving sheet, or other image support substrate, from the belt after the developing material has been transferred from the belt to the receiving sheet. In particular, the stripper roller provides a sharp bend in the path of the rotating belt, such as about ninety degrees for example, which assists in separating or de-tacking of the receiving sheet after image transfer. After being stripped from the belt, the receiving sheet can be directed to or through a fuser for permanently affixing the image transferred from the belt to the receiving sheet.
Generally, smaller diameter stripper rollers tend to better perform their intended stripping function. However, smaller diameter stripper rollers also tend to be more flexible, particularly when the axial length of the stripper roller is required to be relatively long, such as may be needed for wide process width belts. Flexible stripper rollers are susceptible to bending caused by the load force applied to the stripper roller by a taught or well-tensioned belt. Bending of the stripper roller can result in poor belt tracking and the formation of wrinkles in the belt, which both can adversely affect the belt's ability to ultimately transfer an image to a receiving sheet. In contrast, larger diameter stripper rollers are less flexible and therefore bend less, but also have a reduced stripping capacity, particularly for lightweight sheets or substrates.
Heretofore, the competing design factors relating to stripper rollers led to the employment of a compromised stripper roller. The need for a smaller diameter stripper roller to better de-tack from the belt was balanced with the need for a more rigid (i.e., less flexible and bendable) stripper roller to prevent poor belt tracking and/or the formation of wrinkles in the belt. Accordingly, any improvements which allow stripper rollers to remain of smaller diameter, while simultaneously allowing stripper rollers to be less flexible and bendable under a belt load are considered desirable.